In the parent case, an air conditioning system for a grocery store having refrigerated food displays along certain aisles of the store is disclosed. Air outlet diffuser units are mounted in the ceiling of the store and positioned substantially above the aisles adjacent the refrigerated food displays. These diffuser units are constructed to provide a downward flow of conditioned air into the store in such a manner that the shoppers moving about the aisles therebelow receive conditioned air substantially free of drafts for aiding in shopper comfort. The diffuser units are disclosed as including a housing with an outwardly stepped lip configuration defining the air exit mouth. Means defining a tubular air passageway is positioned coaxially of the housing and also defines an annular air passageway therebetween. A plurality of vanes are mounted in the annular passageway for producing rotational, highly turbulent currents of air. Means associated with the tubular air passageway controls the volume of air passing therethrough and also controls the flow pattern of air flowing from the annular air passageway so that as the volume of air passing through the tubular air passageway is increased, the current of air discharged from the annular air passageway is directed downwardly in a more vertical direction.
The stepped exit mouth and lower end of the annular air passageway of each diffuser unit extend below the ceiling surface approximately three inches to minimize the development of a partial vacuum between the jet of discharged air and the ceiling surface which would cause the jet of discharged air to flow along the ceiling surface in an undesirable coanda effect. Additionally, the stepped configuration at the outlet provides a disrupted surface for effecting a more downwardly directed flow of conditioned air exiting from the annular passageway into the grocery store. Air exiting the annular passageway tends to follow the initial, outwardly curved, inside surface of the housing. When the exiting air contacts the disrupted, stepped surface, this gentle flow is disrupted, and as a result, the air flow is directed downwardly instead of horizontally. An annular air control flange is movable relative to the annular passageway to maintain a desired velocity of air along the stepped surface so that when the amount of air flowing through the annular passageway is decreased, the velocity of air engaging the stepped surface is maintained to effect the desired disruption and provide a more downwardly flow of air thereat.
The foregoing air diffuser unit is well suited for use in grocery stores where the ceiling height can extend to heights of twelve to fifteen feet and more. Fifteen foot grocery store ceilings are not uncommon. The stepped configuration at the housing outlet provides the necessary disruption to the air flow for effecting a more downward flow of air. However, one drawback of the aforementioned diffuser design is that the stepped outlet does not provide for much horizontal air flow except when air flow through the tubular air passageway is minimized. At times, it may be more desirable to have some horizontal discharge of air exiting the annular air passageway when the air flow through the tubular air passageway is at a maximum. A horizontal discharge of air would effect a more bell-shaped air flow distribution and effect mixing over an extended aisle surface area. As a result, the total number of air diffusers positioned above the aisles can be reduced because the diffusers can be more spaced-apart. One possible drawback of increasing the horizontal discharge from the diffuser is that the effective vertical throw of air discharged from the diffuser will be reduced. However, where the grocery store ceiling height is about 12 feet or less, it is believed that the reduction in vertical discharge will not adversely affect the successful operation of the air conditioning system. A more bell-shaped air flow distribution having a reduced vertical throw of air therefrom will still provide a downward flow of air into an aisle to induce upwardly the heavy, cool, stagnant air lying adjacent the refrigerated food displays when the grocery store ceiling heights are limited, i.e. about 12 feet or less.
One similar air diffuser design disclosed in German Gebrauchmuster 8,003,910, Feb. 14, 1980, Belgium Patent No. 886,544, Apr. 1, 1981, and Swiss patent No. 648,923, Apr. 15, 1985, includes a rounded instead of a stepped outlet. The rounded outlet always provides some horizontal discharge of air outwardly from the annular air passageway. The rounded outlet provides a smooth, uninterrupted surface on which a small vacuum can be created between the surface and the exiting air so that some air will flow along the rounded surface and then outwardly in a horizontal direction therefrom.
It has heretofore been considered impracticable to use the rounded outlet diffuser units with grocery store ceilings which typically are high ceilings because the rounded outlet always provides for some horizontal discharge of air, thus diminishing the extent of the vertical throw necessary with high ceilings. The disclosed diffuser is also expensive because it uses a servo motor to control the plug-like valve of the opening in the axial passageway and incorporates a movable, annular flange mounted to the lower end of the tubular air passageway means which is movable in unison with the plug-like valve. A more simple diffuser unit construction would be advantageous.
It is therefore an object of this invention to provide an air conditioning system for a grocery store or the like having refrigerated food displays or the like along certain aisles of the store and ceiling mounted air outlet diffuser units mounted in the ceiling for providing a downward flow of conditioned air into the store wherein a plurality of the air outlet diffuser units are each constructed and positioned in the store so that each diffuser unit provides a downward flow of conditioned air over an extended area of the aisle in such a manner that the shoppers moving about the aisles therebelow receive conditioned air substantially free of drafts for aiding in shopper comfort, while heavy, cool, stagnant air lying adjacent the refrigerated food displays and the like is induced upwardly into upper regions of the store above the shoppers for effecting mixing thereof in the upper regions of the store with the conditioned air flowing from the diffuser units and also for mixing with that higher temperature air inherently residing in the upper regions of the store above the shoppers.
It is still another object of the present invention to provide a ceiling mounted air diffuser unit of the aforementioned type which is adapted for use with a grocery store air conditioning system and which is constructed to provide a flow of downwardly directed air over a greater surface area therebelow in such a manner that shoppers moving about the aisles therebelow receive conditioned air substantially free of drafts for aiding in shopper comfort, while heavy, cold, stagnant air lying adjacent the refrigerated food displays and the like is induced upwardly into upper regions of the store about the shoppers for effecting mixing thereof.